Here is the OA for all the questions (OG 10th):

80.
This question asks you to identify the primary focus of the passage.
The best answer is B. The author describes the new theoretical model in the first paragraph; in the
final paragraph the author states that the data obtained from actual observations, which are
discussed in the second and third paragraphs, is consistent with the new theoretical model.
Choice A is not correct; the computer model confirmed the astronomers’ hypothesis that meteor
streams broaden with time, and although the model yielded an unexpected result, the passage does
not contrast the predictions yielded by competing theories. Choice C and D are not correct because
the passage makes no reference to further areas for research, and only a single phenomenon is
described in the passage. And choice E is not correct because it reverses the order of events. The
model yielded a prediction that was subsequently confirmed by observational data, the model was
not constructed to explain the data.
81.
This question asks you to identify an accurate statement about meteor streams. Choice C, the best
answer, restates information about the composition of meteor streams from the first sentence of
the passage.
Choice A is not correct. The passage discusses the influence of planetary gravitation on meteor
streams but says nothing about its influence on the orbits of comets. According to the passage, it is
planetary gravitation, not the gravitational fields of comets, that causes meteor streams to increase
in size, so choice B is not correct. And choice D and E are not correct answers because the passage
says nothing about the composition of comets or the role that meteor streams play in their further
disintegration.
82.
This question asks what the author says about the purpose of the research described in the first
paragraph.
The best answer is D. According to the author, the purpose of the computer-modeling experiment
was to test the hypothesis that meteor streams broaden with time.
Choice A is not correct; although the observational data described in the last paragraph allowed
scientists to estimate the age of the Geminid stream, this data was analyzed to confirm a surprising
prediction made by the computer model. This analysis was not part of the original experiment.
Choice B is also incorrect. Although the experiment yielded a surprising prediction about a
particular feature of meteor streams, the purpose of the experiment was to determine whether
meteor streams broaden with time, not to identify the various structural features of meteor streams.
Choice C is not correct because the experiment was undertaken to test a general hypothesis about
meteor streams. It was not undertaken to explore the nature of any particular meteor stream, and
328
the passage never suggests that the actual meteor streams used in the computer model was
“particularly interesting.”
Choice E is not correct. Although the computer model did confirm the astronomers’ hypothesis,
the purpose of the experiment was not to show that such models are useful.
83.
This question asks you to make an inference about what would most probably be observed during
the Earth’s passage through a meteor stream if the conventional theories mentioned in the passage
were correct. According to line 18-20, the conventional theories predicted that the meteor stream
would be most dense at the center. The computer model, one the other hand, predicted that a
meteor stream would come to resemble a thick-walled, hollow pipe (lines 21-22). The passage
states that, if the computer model were correct, two peak periods of meteor activity would be
observed as the Earth passed through the walls of the “pipe” (lines 28-31). According to lines
36-38, observational data confirmed the prediction of the computer model. If, on the other hand,
the conventional theories were correct, it can be inferred that a bifurcation of meteor activity
would not be observed; instead, it can be inferred that scientists would expect to observe a single
peak of meteor activity as the Earth passed through the dense center of the stream. Choice A
identifies this single peak of activity as the most likely observation if the conventional theories
were correct.
Choice B and D are not correct because they describe meteor activity that is either steady or
erratic, neither of which is consistent with the conventional theories. Choice C describes meteor
activity more in line with the bifurcation predicted by the computer model, rather than the single
peak of activity that the conventional theories would suggest. Choice E is incorrect because the
passage says that meteor showers occur whenever the Earth passes through a meteor stream; it
cannot be inferred that either theory would predict otherwise.
84.
This question asks for the reason given in the passage for a characteristic feature of meteor
streams. According to lines 1-7, the dust particles in a meteor stream eventually surround a
comet’s original orbit because of the different velocities at which they are ejected, as stated in
choice A, the best answer.
Choice B is directly contradicted by information in the passage (lines 8-10). The other answer
choices re incorrect because the passage does not say that the dust particles become part of the
meteor stream at different times, or that their velocity slows over time, or that their ejection
velocity is slower than that of the comet.
85.
This question asks you to identify a prediction that can be derived from both the conventional
theories about meteor streams and the new computer-derived model. You must base your answer
on information that is suggested by, but not expressly stated in, the passage.
According to lines 7-8 of the passage, the conventional theories hypothesized that meteor streams
should broaden with time, and the computer simulation confirmed this hypothesis. The passage
also suggests that the time it takes for the Earth to cross a meteor stream (and, by implication, the
duration of the resulting meteor shower) is directly related to the breadth of the stream (lines
23-28). From these pieces of information, which are supported by both the conventional theories
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and the new computer-derived theory, it can be inferred that on average the meteor showers
caused by older (and therefore broader) meteor streams would be longer in duration than those
caused by very young (and therefore narrower) meteor streams, as stated in D, the best answer.
Choice A is incorrect because it contradicts the predictions of both the conventional theories (that
the particles will be most dense at the center of the stream) and the computer model (that the
stream will resemble a thick-walled, hollow pipe). Choice C is also incorrect because it is
inconsistent with the conventional theories that suggested the distribution of dust in a meteor
stream is denser at the center. And choices B and E are incorrect because the theories discussed in
the passage do not suggest anything about the likelihood that the Earth’s orbit will cross that of
any particular meteor stream, nor do they suggest anything about the size of the dust particles that
compose meteor streams.
86.
This question asks you to draw an inference from information in the last paragraph of the passage.
The best answer is C. According to the passage, the Geminid meteor shower occurs yearly;
because meteor showers occur whenever the Earth passes through a meteor stream, one can infer
that the Earth crosses the Geminid stream once every year.
Choice A is incorrect because the passage provides no information from which to generalize about
the age of meteor streams. Choice B, which is directly contradicted by lines 31-32, is also
incorrect. Choice D is incorrect. In lines 25-28, the passage says that the Earth would take just
over a day to cross the stream if the stream were 5,000 years old. However, in lines 38-42 the
passage states that in fact an average of only 19 houses elapsed between the time that the Earth
entered the stream until the time that it exited, leading researchers to conclude that the stream is
only about 3,000 years old. Choice E is incorrect because the passage says only that planetary
gravitational fields perturb the orbits of dust particles in a meteor stream; it does not say that the
effect of the Earth’s gravitation is greater than that of other planets.
87.
This question asks you to identify an assumption underlying the last sentence of the passage. In
this sentence, the author of the passage draws a conclusion about the age of the Geminid stream.
This conclusion is based on two pieces of information. The first is the length of time the Earth
would take to cross the computer-model Geminid stream if the stream were 5,000 years old (lines
24-28). The second is the actual elapsed time between the two peaks of meteor activity predicted
by the computer model (lines 36-40). In concluding from this information that the Geminid stream
is actually only 3,000 years old, the author is assuming the accuracy of the computer model, as
stated in E, the best answer.
Choice A is incorrect because the passage says that the time the Earth takes to cross the stream
would vary from year to year (lines 32-34) and that 19 hours was the average time, not the exact
time, observed from 1970 to 1979 (lines 36-40). Choices B and C are incorrect because the
passage does not suggest anything about the current state of the comet associated with the
Geminid stream or about the expected longevity of the stream. Choices D is incorrect because the
computer model is said to confirm the broadening predicted by the conventional theories; the fact
that the model projected the positions of the particles in the stream over a 5,000-year period does
not suggest that researchers expected the stream to be older (and therefore broader) than it turned
out to be.

IMAGINE

a big hollow pipe

Now earth can pass through the centre,
Earth can also pass making a chord of a circle

Right??

When Earth passes through the centre, the average time will be x
when it passes somewhere other than the centre, the average time will be less than x

I hope you understood the twin peak shower, when earth passes through the circle


If I was quick and helpful, I'd love to see your gratitude in form of a like to this post.

Glad to help Meisme

DiyaDutta
LOOK Carefully
(A) Most meteor streams it encounters are more than 2,000 years old.
TRICKSTER!!! Last sentence says 3000 yr old

(B) When passing through a meteor stream, it usually passes near to the stream’s center.
There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.

(C) It crosses the Geminid meteor stream once every year.
KEEP IT, couldn't find negation


(D) It usually takes over a day to cross the actual Geminid meteor stream.
a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst

(E) It accounts for most of the gravitational perturbation affecting the Geminid meteor stream.
MOST OF THE???

I hope I was helpful, and if I was, your gratitude in the form of a like to my post is very valuable